Study on thermal control of x-ray mask during post-exposure bake

摘要

The temperature distribution on the surface of the mask, during post exposure bake (PEB) of the X-ray mask after electron beam writing (EBW), is very important for controlling the mask critical dimension(CD). In this paper, three-dimensional finite element (FE) thermal model of the X-ray mask has been set up. The results of the numerical simulation indicate that it will take 2.16 seconds for PEB to get thermal steady when the boundary conditions of the top surface of the resist are natural convections, and that the temperature distribution of the mask is non-uniform, and the maximum temperature difference is 10.19°C, which will most likely make the resist at the high temperature region baked excessively. By using insulation measures, the boundary conditions of the top surface of the resist are changed to adiabatic conditions, and the temperature distribution of the mask is very uniform, which will reduce the influence on the absorber CD from PEB.